Why use genuine Nikon lens caps and
why label them...
A Nikon tech rep told me about Nikon lens caps in the 1980s: how these were engineered, how the plastic was specifically selected for its characteristics, etc. Some aspects of our conversation always stayed with me, when he said that the LF-1 rear lens cap was made to absorb the shock of an impact before breaking or that the front lens caps were made to deflect the energy of an impact and lessen the impact.
At the time, I accepted the advise but did not put much weight on the specifics, I liked Nikon caps as they felt like quality.
Recently I had a 400mm f2.8 Nikkor shipped to me. Despite my plea to package it well, it was not. The cardboard box looked like it had been dropped from the plane straight onto the ground. The impact force must have been significant, to put it mildly, as the lens shifted in the box and all the energy was absorbed by the Nikon LF-1 rear cap. The results were stunning, the box and cap were demolished, but the lens was intact without any damage. The LF-1 "Made in Japan" cap performed at its best. The vintage "Made in Japan" Nikon caps are all made to high quality standards and should not be substituted. I can not speak about modern caps made in China as I avoid Chinese products due to their inferior quality.
My conversation with the Nikon rep was 30 years ago but proves that good advise remains timeless.
There are considerable advantages in labeling your lens caps, not only will it help select and identify a lens quickly when you have many lenses, it gives you a quick reminder about the (custom) setting to use with the lens.
I use lenses for specific applications where I use the lenses' features and qualities to the fullest. Each lens will have its own characteristics including how it meters. Adding an exposure compensation value on your caps can help you dial that in at the time you mount the lens instead of just relying on memory. Often exposure (compensation) can also be a matter of personal taste… Color coding the information can further simplify the process, blue for negative values, red for positive, or whatever works best for you.